1. Field of the Invention
The present invention relates to an arrangement for increasing the roll stability of rail vehicles which are equipped with air suspension.
2. Description of the Prior Art
It is known to control air spring bellows, which serve for the secondary suspension of rail vehicles, in such a manner that track twist will not affect derailing safety despite the torsional stiffness of a car body. To this end, the lateral air spring bellows of a first bogie are controlled by separate leveling valves, so that the car body is always kept approximately parallel to the bogie underneath it. The air spring bellows of a second bogie, however, are only controlled by a leveling valve arranged mid-way between the air spring bellows, so that while on the average the level corresponds to that of the air spring bellows of the first bogie, oscillating or swinging motions of the second bogie about its longitudinal axis under the car body are possible, so that track twist can be negotiated without any torsional deflection of the car body being necessary. Although this takes care of derailing safety of the car, such features fail to maintain satisfactory roll stability in certain cases, especially in the case of vehicles operating on a narrow track gauge where the supporting base of the air spring bellows is reduced (German Offenlegungsschrift No. 28 30 359).
It is also known to equip both bogies under a car body with roll stabilizers. It is common practice to have the roll stabilizer formed as a torsion bar which is rotatably supported in a bogie frame and is connected at both ends to the car body by means of horizontally positioned levers and vertically positioned links. While such a system is suitable to limit roll motions, it automatically interferes with the ability of both bogies to swing about their longitudinal axes, so that they cannot match track twist to the desired extent and, consequently, are susceptible to derailing where the car bodies are torsionally stiff.
In the case of bogies equipped with air suspension, it is known to provide an emergency support system on three points. In this arrangement, the emergency support of a first bogie takes the form of a rubber- bonded- metal composite spring integrated in each air spring bellows. The emergency support of the second bogie relies on an emergency spring positioned at the center pivot. This emergency spring may be formed as a coil spring or as a spring with elastomeric material. The clearance of this emergency support relative to the vertical travel of the air springs of this bogie is selected such that on deviation of either air bellows, the emergency spring will be first to take the load, and that the ability of this bogie to swing about its longitudinal axis is sufficient to enable it to match the usual track twist without any constraint. The drawback of this system is the insufficient roll stability of the air spring bellows (German Utility Patent No. 81 37 758).
In contrast to this, it is the object of the present invention to control roll motions without simultaneously reducing derailing safety.